• Article

Convert.ToDouble Method (String)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Converts the specified String representation of a number to an equivalent double-precision floating point number.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Shared Function ToDouble ( _
    value As String _
) As Double

public static double ToDouble(
    string value
)

Parameters

Return Value

Type: System.Double
A double-precision floating point number equivalent to the value of value.
-or-
Zero if value is nulla null reference (Nothing in Visual Basic).

Exceptions

Exception Condition
FormatException

value is not a number in a valid format.
OverflowException

value represents a number less than MinValue or greater than MaxValue.

Remarks

The return value is the result of invoking the Double.Parse method on value.

If you prefer not to handle an exception if the conversion fails, you can call the Double.TryParse method instead. It returns a Boolean value that indicates whether the conversion succeeded or failed.

Examples

The following code sample illustrates the conversion of a String value to a Double one, using ToDouble.

Public Sub CovertDoubleFloat(ByVal doubleVal As Double)
   Dim singleVal As Single = 0

   ' Double to Single conversion cannot overflow.
   singleVal = System.Convert.ToSingle(doubleVal)
   outputBlock.Text &= String.Format("{0} as a Single is {1}", _
                             doubleVal, singleVal) & vbCrLf

   ' Conversion from Single to Double cannot overflow.
   doubleVal = System.Convert.ToDouble(singleVal)
   outputBlock.Text &= String.Format("{0} as a Double is: {1}", _
                             singleVal, doubleVal) & vbCrLf
End Sub


...


Public Sub ConvertDoubleString(ByVal doubleVal As Double)

   Dim stringVal As String

   ' A conversion from Double to String cannot overflow.       
   stringVal = System.Convert.ToString(doubleVal)
   outputBlock.Text &= String.Format("{0} as a String is: {1}", _
                             doubleVal, stringVal) & vbCrLf

   Try
      doubleVal = System.Convert.ToDouble(stringVal)
      outputBlock.Text &= String.Format("{0} as a Double is: {1}", _
                                stringVal, doubleVal) & vbCrLf
   Catch exception As System.OverflowException
      outputBlock.Text &= String.Format( _
          "Overflow in String-to-Double conversion.") & vbCrLf
   Catch exception As System.FormatException
      outputBlock.Text &= String.Format( _
          "The string is not formatted as a Double.") & vbCrLf
   Catch exception As System.ArgumentException
      outputBlock.Text &= "The string is null." & vbCrLf
   End Try

End Sub

public void CovertDoubleFloat(double doubleVal)
{
   float floatVal = 0;

   // Double to float conversion cannot overflow.
   floatVal = System.Convert.ToSingle(doubleVal);
   outputBlock.Text += String.Format("{0} as a float is {1}",
      doubleVal, floatVal) + "\n";

   // Conversion from float to double cannot overflow.
   doubleVal = System.Convert.ToDouble(floatVal);
   outputBlock.Text += String.Format("{0} as a double is: {1}",
      floatVal, doubleVal) + "\n";
}


...


public void ConvertDoubleString(double doubleVal)
{
   string stringVal;

   // A conversion from Double to string cannot overflow.       
   stringVal = System.Convert.ToString(doubleVal);
   outputBlock.Text += String.Format("{0} as a string is: {1}",
      doubleVal, stringVal) + "\n";

   try
   {
      doubleVal = System.Convert.ToDouble(stringVal);
      outputBlock.Text += String.Format("{0} as a double is: {1}",
         stringVal, doubleVal) + "\n";
   }
   catch (System.OverflowException)
   {
      outputBlock.Text += String.Format(
         "Conversion from string-to-double overflowed.") + "\n";
   }
   catch (System.FormatException)
   {
      outputBlock.Text += String.Format(
         "The string was not formatted as a double.") + "\n";
   }
   catch (System.ArgumentException)
   {
      outputBlock.Text += String.Format(
         "The string pointed to null.") + "\n";
   }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.